code: def step(self, *, noise_multiplier: float, sample_rate: float):
      if len(self.history) >= 1:
          (
              last_noise_multiplier,
              last_sample_rate,
              num_steps,
          ) = self.history.pop()
          if (
              last_noise_multiplier != noise_multiplier
              or last_sample_rate != sample_rate
          ):
              raise ValueError(
                  "Noise multiplier and sample rate have to stay constant in GaussianAccountant."
              )
          else:
              self.history = [
                  (
                      last_noise_multiplier,
                      last_sample_rate,
                      num_steps + 1,
                  )
              ]
  
      else:
          self.history = [(noise_multiplier, sample_rate, 1)]
  
file_path: opacus/opacus/accountants/gdp.py
imports: import warnings
  from .accountant import IAccountant
  from .analysis import gdp
label_desc: Use image node_id 2 for calling the GaussianAccountant obj's underlying member method code with example usage: obj.step() without return types